Scientists conduct investigations or experiments that are often categorized as “in vivo” or “in vitro”. For purposes of this application, the term “in vivo” means “in the living” and “in vivo experiments” are experiments conducted using complete living organisms. An example of an in vivo experiment includes administering a drug to a human or a live mouse and observing or testing whether the drug has the intended effect and/or any side effects.
The term “in vitro” means “in the glass”, for example, in a test tube or in a petri dish. As such, in vitro experiments are experiments conducted not within a non-living organism but instead on only part of an organism, such as cells or biological molecules, or outside the organism's normal biological context.
For purposes of this application, the term “subject” will be used to refer that to which an experiment is directed such as cells, groups of cells, tissues, organs, entire organisms, or any other biological subject of experimentation.
An advantage of in vivo experiments is that the subject of the experimentation is still operating within the subject's normal biological context (e.g., in a population or ecosystem). Accordingly, any experimental manipulations performed in vivo are considered to be most representative of the situation under observation or review. However, often such experiments are not practical or not considered ethical. Therefore, in vitro experiments are sometimes used as a substitute.
For example, when a scientist wishes to study a subject in vitro, he or she may remove representative cells, groups of cells, or portion from an organism, then observe the isolated subject, and possibly introduce some experimental variable. Introducing an experimental variable may include changing something in the surroundings (e.g., temperature, pressure, light conditions, concentration of certain chemicals in an aquatic environment), or involve the administration of a substance to which a subject is not typically exposed. After introducing the variable, the scientist may observe or otherwise assess, detect, or measure whether any change has occurred in the subject. If there is a change in the subject, it may be caused by or at least be correlated with the introduction of the experimental variable.
In certain experiments, scientists may attempt to control the factors that are not being studied as the variable in order to minimize or eliminate any effect on the subject caused by those factors. This is generally easier to do in vitro with an isolated subject than in an entire living organism. Scientists may attempt also to simulate the conditions for a subject in vivo, and, accordingly, facilitate observing any effect or correlation resulting from treatment with the variable.
Certain devices have been developed to facilitate controlling the in vitro environment and simulating in vivo conditions. For example, when a subject is a cell or a tissue, a scientist may wish to observe or treat the subject while it is alive. A cell or tissue subject may need certain chemicals, gases, nutrients, or other requirements to stay alive and possibly grow. Examples of such requirements are glucose or pyruvate, for cellular energy sources, myo-inositol for intracellular calcium control and maintenance of membrane potentials, oxygen to sustain the aerobic metabolism, or growth factors. Accordingly, the device in such circumstances may be in a dish in which the subject cell or cell tissue is positioned in a solution containing at least the chemicals, gases, and/or nutrients that are needed by the subject to be kept in the condition required for the experiment. This solution containing at least the required or critical components will be termed “nutrient solution” for purposes of this application. Anyone of such required components may be generically identified in this application as a “nutrient”.
As time passes, the cell/tissue that is the subject of the experiment may consume one or more of a critical component, such as oxygen or glucose, from the nutrient solution. Accordingly, the concentration of the critical component in the solution may decrease. For example, many experimental subjects require oxygen or carbon dioxide to maintain cellular processes. Because the concentration of this gaseous nutrient will decrease over time in the nutrient solution, certain known devices are configured to permit the nutrient solution to be “bubbled” with oxygen or carbon dioxide, However, many such known devices do not facilitate the atmospheric conditions associated with the nutrient solution to be monitored and managed. As a result, the balance of such a critical component relative to the solution may be altered over time and, for example, the cellular processes to be affected or the pH of the solution to become imbalanced.
Alternatively, certain known devices attempt to manage the issue of a loss of one or more critical component in the device over time by permitting the original nutrient solution to be released from the dish after a certain period of time, and discarded. Additional nutrient solution may then be permitted to flow into the dish from a storage container. Some other known devices achieve this same goal by establishing a continuous inflow of solution from an external reservoir and matching outflow. In such other known devices, fresh nutrient solution enters the device from one side while spent nutrient solution exits the device from the opposite side, establishing a continuous unidirectional flow of nutrient solution across the subject of the experiment. While these types of devices and replenishment systems may keep the subject cell or tissue exposed to the necessary components in the appropriate concentration, the components of the nutrient solution not consumed by the cell or tissue are discarded generally as waste. Discarding all the nutrient solution, including those components that were not consumed, altered, or made ineffective during the course of the experiment is especially problematic when one or more of the components of the solution are rare, expensive, or otherwise difficult to mix or maintain.
Whenever nutrient solution is valuable, the amount that is used and possibly wasted must be reduced. Certain techniques and devices have been developed in order to achieve this objective, some of which are the following. One technique reduces the rate at which solution enters and leaves the device, thereby reducing the overall consumption of nutrient solution. Another technique and device does not discard the spent solution exiting the device but instead collects and recycles it.
However, many known devices and techniques that seek to improve the efficiencies of in vitro experimentation have one or more disadvantages associated with them. For example, the techniques and devices that seek to collect and recycle spent solution largely all require a variety of additional components with which the complete volume of solution that was in the experimental area can exit the area and be held and processed—including to add in any nutrient that may have been depleted during the experiment—and the processed solution added back into the experimental area. The need for such additional components—such as tubing, containers, and pumps—all add to the cost of the experiment. Also, in order to establish the needed fluid circulation from the experimental area through these additional collection and recycling components and back to the experimental area, a volume of nutrient solution much larger than the amount needed in the immediate experimental area is required. Even the most volume-conservative existing devices require a total fluid volume of at least 8-10 ml in order to establish fluid circulation. If the nutrient solution or at least a component of the nutrient solution is rare, expensive, or otherwise difficult to obtain, 8-10 mL may be an amount that is larger than that which can be readily prepared.
Clearly, there is a demand for a more efficient and cost effective system and methods to manage the nutrient solutions used in experimentation. The present invention satisfies this demand.